A copper base material having excellent electric and heat conductibility has been used as a semiconductor lead frame material or a terminal and connector material, widely. As a trend of fabrication of devices heads for high density integration, or fabrication of a smaller device, besides the electric and heat conductibility, a high conductibility copper alloy with an excellent surface state, such as high elongation and high platability which is required for workability is in demand, more strongly.
To deal with this, even though different copper alloys have been developed, there have been difficulties for preparing an excellent Cu—Cr base alloy as a high conductibility copper alloy, including a problem of preparing the Cu—Cr base alloy at a low cost, and in a high quality and high yield, easily.
Japanese Patent Laid Open Publication No. 2003-89832 (Hereafter, “a prior art 1”) discloses molten metal of 0.02˜0.4 wt % of Cr, 0.01˜0.3 wt % of Zn, 0.005˜1.0 wt % of at least one of Ti, Ni, Fe, Sn, Si, Mn, Co, Al, B, In and Ag, and a balance of Cu, prepared by subjecting an ingot from the molten metal to steps of hot rolling, solution treatment, cold rolling, ageing, cold rolling, annealing, and processing a raw material obtained with above steps to meet a required thickness, to obtain a product, in claim 4.
However, the copper alloy of the prior art 1 comprises, not Cr, but Zr, as a component, and has inadequate tensile strength even though conductivity thereof is high, and it is not clear how a physical property value on the elongation required for workability is reached while maintaining the tensile strength, and how hardness is reached while all of above physical property values are maintained, at all.
And, Japanese Patent Laid Open Publication No. 2001-181757 (Hereafter, “a prior art 2”) discloses a copper alloy consisting of 0.2˜0.35 wt % of Cr, 0.1˜0.5 wt % of Sn, 0.1˜0.5 wt % of Zn, 0.05˜0.1 wt % of Si, at least one of Pb, Bi, Ca, Sr, Te, Se, and a rare earth element, and a balance of Cu, prepared by subjecting an ingot of molten metal of above composition to steps of heating to 880˜980° C., hot rolling, cold rolling, and ageing at 360˜470° C. before or after the cold rolling, to obtain a copper alloy having excellent blanking workability.
The prior arts secure characteristics of strength and conductibility by controlling solid solution and precipitateion of, mainly, a Cr or Cr—Si base compound by steps of hot rolling, cold rolling, solution treatment, and ageing, and so on.
In the prior art 2, if a copper alloy with around 0.3˜0.4 wt % of Cr content is prepared without a high temperature solution treatment, a final rolled plate has many of a few tens μm of Stringer phases, or a few μm sized granular precipitates formed therein, affecting platablity by defects due to these or by difference of chemical properties of the precipitates and a Cu matrix.
And, Japanese Patent Laid Open Publication No. H7-54079 (Hereafter, “a prior art 3”) discloses composition consisting of 0.01˜0.2 wt % of Cr, 0.005˜1 wt % of Zr, and as miscellaneous elements, 0.005˜10 wt % of Ni, Sn, and Zn respectively, 0.005˜5 wt % of Fe, Co, Te, and Nb respectively, 0.001˜2 wt % of Be, Mg, Mo, W, Y, Ta, and rare earth elements respectively, 0.001˜10 wt % of Mn and Al respectively, 0.001˜5 wt % of Si, Ge, V, Cd, Hf, Sb, and Ga respectively, 0.001˜3 wt % of Ag, and 0.001˜1 wt % of B and P, respectively.
And, the prior art 3 intends to improve strength and electric conductivity by subjecting an ingot from molten metal of above composition to steps of hot rolling, solution treatment, ageing, and so on. The prior art 3 takes 35 kinds of miscellaneous elements as components.
That is, while families on the periodic table are 15 families in total including IA family˜VIII family (8 families) and IB family˜VIIA family (7 families), the prior art 3 takes elements belonging to 10 families excluding IA family (Alkali metal), HA family (Alkali earth family: four elements excluding Be and Mg), VIIA (Halogen family), VIA family (Oxygen family), and VA family (Nitrogen family) as components. However, table 1, illustrated Embodiments, not only discloses a Cu—Cr base, a Cu—Zr base, or a Cu—Cr—Zr base as components, wherein the Cu—Cr base alloys (Embodiments 1˜5) are added by Ni, B, Fe, and P as the miscellaneous elements, the Cu—Zr base alloys (Embodiments 6˜9) are added by Mg, Ag, and Be as the miscellaneous elements, and the Cu—Cr—Zr base alloys (Embodiments 10˜22) are added by one kind (Embodiments 11˜15, and 22), two kinds (Embodiments 16˜17), or three kinds (Embodiments 18˜21) as the miscellaneous elements, but also shows no information on the tensile strength at all and unclear information on the conductivity.
However, the prior art 3 has a problem in that, though the prior art 3 describes that as if all of the 25 kinds of elements are equivalent substances accompanying identical or similar effects by including the 25 kinds of elements as the miscellaneous materials, as made it clear in description of the embodiments, it is apparent that the technical constitution of the prior art 3 is actually limited to the embodiments.
Therefore, the prior art 3 has a limitation in having both the high conductibility and the high elongation at a time while improving or maintaining the tensile strength, and a problem in that the solution treatment accompanied in preparation of the copper alloy is a production cost increasing factor.
In the meantime, Korean Patent Application No. 10-2009-0004626 (Hereafter, “Prior Art 4”) discloses an alloy consisting of 0.2˜0.4 wt % of Cr, 0.05˜0.4 wt % of Sn, 0.05˜0.4 wt % of Zn, 0.01˜0.05 wt % of Si, 0.003˜0.02 wt % of P and Mn, and a balance of Cu.
In order to develop an alloy having excellent characteristics better than the strength and electric conductivity of the alloy of the prior art 4, Mg is added to the composition illustrated in embodiments of the prior art to invent a method for preparing a copper alloy having high strength, high workability, and high conductibility.